In this paper, we define the notion of a bipolar general fuzzy automaton, then we construct some closure operators on the set of states of a bipolar general fuzzy automaton. Also, we construct some topologies on the set of states of a bipolar general fuzzy automaton. Then we obtain some relationships between them.

We study the sofic tree shifts of A ∗ , where Σ∗ is a regular rooted tree of finite rank. In particular, we give their characterization in terms of unrestricted Rabin automata. We show that if X ⊂ A ∗ is a sofic tree shift, then the configurations in X whose orbit under the shift action is finite are dense in X , and, as a consequence of this, we deduce that every injective cellular automata τ ...

Pebble tree-walking automata with alternation were first investigated by Milo, Suciu and Vianu (2003), who showed that tree languages recognized by these devices are exactly the regular tree languages. We strengthen this by proving the same result for pebble automata with “strong pebble handling” which means that pebbles can be lifted independently of the position of the reading head and withou...

We consider several questions about monotone AC-tree automata, a class of equational tree automata [21] whose transition rules correspond to rules in Kuroda normal form of context-sensitive grammars. Whereas it is known that this class has a decision procedure to determine if a given monotone AC-tree automaton accepts no term [23], other decidability and complexity results have not been well-in...